This invention relates to a method of selecting a transport format combination (TFC) and to a mobile terminal apparatus. More particularly, the invention relates to a TFC selection method for performing a TFC selection in such a manner that maximum transmission power of the apparatus will not be exceeded or in such a manner that an appropriate transmission power will be obtained, and to a mobile terminal that employs this method.
FIG. 13 is a block diagram illustrating a CDMA mobile terminal device according to the prior art. User data and control data, sent from a plurality of terminal access function units (abbreviated to “TAF” below) 1a to in and a host application 2 upon being mapped to prescribed local channels (abbreviated to “LCH” below), is collected together in a terminal access function interface (abbreviated to “TAF IF” below) 3. The TAF IF 3 has a TFC decision unit 3a for checking the state of a connection between an LCH and a transport channel (abbreviated to “TrCH” below) from connection information designated beforehand by a higher layer. If the LCH has been connected to the TrCH, then, in accordance with transport format information (a TFI table) that specifies one or more transport data lengths of prescribed transmission time intervals TTI of the TrCHs designated similarly by the higher layer, the TFC decision unit 3a decides a combination TFC of transport formats of TrCHs capable of transmitting as much data as possible. Here TTI, TFI and TFC are the abbreviations of Transmission Time Interval, Transport Format Indicator and Transport Format Combination, respectively.
The TAF IF 3 has a TrCH data demultiplexer 3b for recognizing transport data length every transmission time interval TTI of each TrCH based upon the TFC that has been decided, separating the transport data of each TrCH every transmission time interval TTI based upon the transport data length, and inputting the separated data to a channel codec. In the description that follows, it is assumed that the number of TrCHs is four and that the TTIs of respective ones of the TrCHs are 10 ms, 20 ms, 40 ms and 80 ms.
Transmit buffers 51 to 54 of the channel codec write the transport data, which enters from the TAF IF 3, to buffer memories (not shown) continuously and read out the transport data every TTI of 10 ms, 20 ms, 40 ms, 80 ms and input the read data to encoding processors 61 to 64, respectively, which constitute the succeeding stage. The encoding processors 61 to 64 encode the transport data of the TTIs 10, 20, 40 and 80 ms in accordance with convolutional or turbo encoding and input the encoded data to a multiplexer 7. More specifically, the encoding processor 61 outputs encoded data E10 having a duration of 10 ms, the encoding processor 62 outputs encoded data E20 having a duration of 20 ms, the encoding processor 63 outputs encoded data E40 having a duration of 40 ms, and the encoding processor 64 outputs encoded data E80 having a duration of 80 ms. For example, as shown in FIG. 14, the encoder 61 outputs encoded data 10 ms-1 every 10 ms, the encoder 62 outputs the first half 20 ms-1 and second half 20 ms-2 of the encoded data E20 in order every 10 ms, the encoder 63 outputs one-quarter portions 40 ms-1, 40 ms-2, 40 ms-3, 40 ms-4 of the encoded data E40 in order every 10 ms, and the encoder 64 outputs one-eighth portions 80 ms-1, 80 ms-2, 80 ms-3, 80 ms-4, 80 ms-5, 80 ms-6, 80 ms-7, 80 ms-8, of the encoded data E80 in order every 10 ms.
The multiplexer 7 multiplexes the encoded data that enters from the encoding processors 61-64 every 10 ms, creates one frame's worth of multiplexed data and inputs the multiplexed encoded data DPDCH to a modulator 9 as in-phase component data. FIG. 14 is a diagram useful in describing the multiplexing method. In the initial 10th millisecond, encoded data {10 ms-1, 20 ms-1, 40 ms-1, 80 ms-1} is multiplexed and transmitted as a first frame. Subsequently, in 20th to 80th milliseconds, the following multiplexed data is created and transmitted as second to eighth frames:                multiplexed data: {10 ms-1, 20 ms-2, 40 ms-2, 80 ms-2} . . . second frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-3, 80 ms-3} . . . third frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-4, 80 ms-4} . . . fourth frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-1, 80 ms-5} . . . fifth frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-2, 80 ms-6} . . . sixth frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-3, 80 ms-7} . . . seventh frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-4, 80 ms-8} . . . eighth frameThat is, transport data of the TrCH for which the transmission time interval TTI is 10 ms is transmitted every frame, transport data of the TrCH for which the transmission time interval TTI is 20 ms is transmitted over two frames, transport data of the TrCH for which the transmission time interval TTI is 40 ms is transmitted over four frames, and transport data of the TrCH for which the transmission time interval TTI is 80 ms is transmitted over eight frames.        
A control signal generator 8 inputs control data DPCCH such as a pilot PILO, TFCI and TPC to the modulator 9 as quadrature-component data at a fixed symbol rate. QPSK spreaders 9a, 9b subject the transport data DPDCH (I-channel component) and control data DPCCH (Q-channel component) to spread-spectrum modulation using a predetermined spreading code, multipliers 9c, 9d multiply the spread data by gain factors βd, βc, which have been calculated by a gain-factor calculation unit 4, the products undergo a DA conversion in a DA converter (not shown), and the resultant analog signals are input to a QPSK quadrature modulator 9e. The latter subjects the I-channel signal and Q-channel signal to QPSK quadrature modulation, and a radio transmitter 10 frequency-converts (IF→RF) the baseband signal from the quadrature modulator 9 to a high-frequency signal, performs high-frequency amplification, etc., and transmits the amplified signal from an antenna ANTT.
FIG. 15 is a diagram useful in describing the frame format of an uplink signal from a mobile station (mobile terminal device) to a base station. One frame has a length of 10 ms and is composed of 15 slots S0 to S14. User data DPDCH (Dedicated Physical Data Channel) is mapped to the orthogonal I channel of QPSK modulation and control data DPCCH (Dedicated Physical Control Channel) is mapped to the orthogonal Q channel of QPSK modulation. The number n of bits in each slot in the I channel for user data varies in dependence upon symbol rate. Each slot in the Q channel for control data is composed of ten bits and the symbol rate is a constant 15 ksps. The user data DPDCH is formed by multiplexing the data of one or more transport channels TrCH, and the control data DPCCH is composed of a TPC (Transmission Power Control) bit, TFCI (Transport Format Combination Indicator), PILOT and FBI (Feedback Information).
FIG. 16 is a diagram useful in describing the frame format and slot arrangement of a downlink signal from a base station to a mobile station. One frame has a length of 10 ms and is composed of 15 slots S0 to S14. Each slot contains a mixture of user data Data 1, Data 2 and control data TPC, TFCI, PILOT. The data in each slot is distributed in turns to the I channel and Q channel of QPSK quadrature modulation one bit at a time, after which spread-spectrum modulation and quadrature modulation are applied, frequency conversion is carried out and the resultant signal is transmitted to the mobile station.
At reception, a radio receiver 12 subjects a high-frequency signal received from an antenna ANTR to a frequency conversion (RF→IF conversion) to obtain a baseband signal, after which a demodulator 13 subjects the baseband signal to quadrature detection to generate an in-phase component (I component) signal and a quadrature component (Q component) signal, applies an analog-to-digital conversion to each of these signals, applies despread processing to the I- and Q-component data using a code identical with that of the spreading code, inputs the user data DPDCH to a demultiplexer 15 of the channel codec and inputs the control data to a TPC extraction unit 14. The latter extracts the TPC bit from the control data DPCCH and inputs this to a transmission power controller 11.
As shown in FIG. 17, the following encoded data that has been multiplexed is input to the demultiplexer 15 frame by frame:                multiplexed data: {10 ms-1, 20 ms-1, 40 ms-1, 80 ms-1} . . . first frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-2, 80 ms-2} . . . second frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-3, 80 ms-3} . . . third frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-4, 80 ms-4} . . . fourth frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-1, 80 ms-5} . . . fifth frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-2, 80 ms-6} . . . sixth frame        multiplexed data: {10 ms-1, 20 ms-1, 40 ms-3, 80 ms-7} . . . seventh frame        multiplexed data: {10 ms-1, 20 ms-2, 40 ms-4, 80 ms-8} . . . eighth frame        
The demultiplexer 15 inputs the initial 10-ms encoded data 10 ms-1 of each frame to a first decoding processor 161, inputs second 20-ms encoded data 20 ms-1, 20 ms-2 to a second decoding processor 162, inputs third 40-ms encoded data 40 ms-1, 40 ms-2, 40 ms-3, 40 ms-4 to a third decoding processor 163, and inputs fourth 80-ms encoded data 80 ms-1, 80 ms-2, 80 ms-3, 80 ms-4, 80 ms-5, 80 ms-6, 80 ms-7, 80 ms-8 to a fourth decoding processor 164. That is, data of the service for which the transmission time interval TTI 10 ms is received frame by frame, data of the service for which the transmission time interval TTI is 20 ms is received over two frames, data of the service for which the transmission time interval TTI is 40 ms is received over four frames and data of the service for which the transmission time interval TTI is 80 ms is received over eight frames.
The first decoding processor 161, which applies error correction processing to the encoded data of length 10 ms and decodes the original transport data, decodes the encoded data 10 ms-1 and inputs the decoded data to a succeeding receive buffer 171 every 10 ms. The second decoding processor 162, which applies error correction processing to the encoded data for which the transmission time interval TTI is 20 ms and decodes the original transport data, decodes the encoded data 20 ms-1, 20 ms-2 and inputs the decoded data to a succeeding receive buffer 172 every 20 ms. The third decoding processor 163, which applies error correction processing to the encoded data for which the transmission time interval TTI is 40 ms and decodes the original transport data, decodes the encoded data 40 ms-1 to 40 ms-4 and inputs the decoded data to a succeeding receive buffer 173 every 40 ms. The fourth decoding processor 164, which applies error correction processing to the encoded data for which the transmission time interval TTI is 80 ms and decodes the original transport data, decodes the encoded data 80 ms-1 to 80 ms-8 and inputs the decoded data to a succeeding receive buffer 174 every 80 ms.
The receive buffers 171, 172, 173 and 174 write the decoded data to buffer memories every 10 ms, 20 ms, 40 ms and 80 ms, read the decoded data out of the buffer memories continuously at a prescribed speed and input the data to the TAF IF 3. The TAF IF 3 selectively inputs the decoded data, which enters from each of the receive buffers 171 to 174, to the TAF units 1a to 1n and host application 2.
Multiplexing and Demultiplexing Control
The above is a description of the overall operation of the mobile terminal. Multiplexing and demultiplexing will be described in greater detail below. The data transceive time intervals of the W-CDMA system are stipulated as being 10, 20, 40 and 80 ms, as mentioned above. Such a time interval is referred to as a TTI (Transmission Time Interval), as pointed out above. The transceive timing is as shown in FIG. 18 on a per-TTI basis.
The encoding processor 6i (i=1 to 4) of the channel codec in this W-CDMA system accepts data transmitted from a higher layer, executes encoding processing on a per-transport-channel (TrCH) basis, multiplexes the encoded data, maps the multiplexed data to a physical channel and transmits the data. Conversely, the decoding processor 16i (i=1 to 4) of the channel codec demultiplexes the data, which has been multiplexed onto the physical channel, on a per-transport-channel (TrCH) basis, executes decoding processing and delivers the results to the TAF IF 3.
When communication starts, information necessary for encoding processing and multiplexed transmission, such as the encoding scheme (convolutional encoding, turbo encoding, etc.), transmission time interval TTI and transport format TFI, are specified for each transport channel (TrCH) by the higher layer in the TAF IF 3. On the basis of bit rate of the transport data of each TrCH and the transport format information (TFI table) of each TrCH specified by the higher layer, the TAF IF 3 decides a combination (transport format combination TFC) of transport data lengths every transmission time interval TTI of the TrCHs, demultiplexes the transport data of each TrCH on a per-TTI basis and inputs the demultiplexed data to the channel codec. The latter performs encoding in accordance with the encoding scheme specified. If transport data is encoded on each transport channel (TrCH), the data is multiplexed frame by frame, mapped to the physical channel and transmitted. The physical-channel data is transmitted in units of 10 ms since one frame has a duration of 10 ms. Accordingly, data having a TTI of 20 ms or greater is divided evenly into frame units of 10 ms each and the data is then transmitted upon being mapped to the physical channel taking the time TTI. FIG. 19 illustrates an example in which two transport channels TrCH#1, TrCH#2 of TTIs 20 ms and 40 ms, respectively, are multiplexed and transmitted (TrCH#1: TTI=20 ms, TrCH#2: TTI=40 ms). In FIG. 19, TrCH#1-1 and TrCH#1-2 of first and second frames are the initial 20 ms of data of TrCH#1, and TrCH#1-3 and TrCH#1-4 of third and fourth frames are the next 20 ms of data of TrCH#1.
When the encoded data of each transport channel (TrCH) is multiplexed, mapped to a physical channel and transmitted, a parameter indicating how the encoded data of each transport channel TrCH has been multiplexed is created in such a manner that demultiplexing can be performed correctly on the receiving side, and this parameter is transmitted upon being attached to the physical-channel data. This parameter is referred to as a TFCI (Transport Format Combination Indicator). The TFCI is uniquely decided by a combination of transport formats which specify the bit length (number of blocks x block length) per TTI of data transmitted by each transport channel (TrCH).
Transport formats are numbered and each is denoted by a TFI (Transport Format Indicator). In FIG. 20, (A), (B) illustrate examples of TFI tables in a case where user data DPDCH is multiplexed and transmitted on transport channel TrCH#1 and transport channel TrCH#2. There are six types of TFIs of TrCH#1 for the user data. These are formats for which the bit lengths per transmission time interval TTI thereof are 0×336 bits, 1×336 bits, 2×336 bits, 4×336 bits, 8×336 bits and 12×336 bits; the TFIs are 0, 1, 2, 3, 4 and 5. Further, there are two types of TFIs of TrCH#2 for the control data. These are formats for which the bit lengths per transmission time interval TTI thereof are 0×148 bits and 1×148, and the TFIs are 0 and 1, respectively.
If the transport channels are only of the two types TrCH#1 and TrCH#2, then the combinations of TFIs of TrCH#1 and TrCH#2 will be a total of 12 (6×2), as shown in (C) of FIG. 20, and a CTFC (Calculated Transport Format Combination) can be calculated for each combination using a CTFC calculation formula. It should be noted that the column on the right side of FIG. 20(C) shows the CTFCs. Since the transmit and receive sides possess a TFCI-CTFC correspondence table shown in (D) of FIG. 20, the transmit side converts a calculated CTFC to a TFCI using this correspondence table, encodes the TFCI and transmits the same. For example, if data for which the number of bits per TTI is 2×336 bits is transmitted from the TrCH#1 over a period of 20 ms, data for which the number of bits per TTI is 1×336 bits is transmitted from the TrCH#1 in succession over a period of 20 ms and data for which the number of bits per TTI is 1×148 bits is transmitted from the TrCH#2 over a period of 40 ms, then four frame's worth of multiplexed data every 10 ms becomes the combinations of TFIs shown in (E) of FIG. 20. Accordingly, the CTFC in each combination is calculated, this CTFC is converted to a TFCI using the correspondence table of FIG. 20(D), and this TFCI is transmitted upon being encoded.
A specific example will be given using FIG. 21. Consider a case where 148-bit data is mapped to LCH0 from the host application 2, 8400-bit data is mapped to LCH1 from the TAF unit 1a and this data is sent to the TAF IF 3. Since the connectable LCHs and TrCHs are {circle around (1)} LCH0 and TrCH1 and {circle around (2)} LCH1 and TrCH2, channel encoding processing is possible on LCH0 as TrCH1 and on LCH1 and TrCH2.
A plurality of transport formats of each TrCH is specified from the higher layer. The transport format indicates the transport data length of the transmission time interval TTI specified in advance from the higher layer, and the transport data length is expressed by transport block count (number of TrBks)×TrBk bit count. The TTI of TrCH1 is 40 ms, the transport formats are of two types, namely 0×148 bits and 1×148 bits, the TTI of TrCH1 is 20 ms, and there are nine types of transport formats, namely 0×336 bits, 1×336 bits, 2×336 bits, 3×336 bits, 4×336 bits, 8×336 bits, 16×336 bits, 20×336 bits and 24×336 bits.
When each TrCH is multiplexed and transmitted, it is necessary to raise throughput as much as possible and therefore a transport format that is capable of transmitting as much data as possible is selected. In the specific example of FIG. 21, the data to be transmitted on LCH0 is 148 bits and the transport formats of TrCH1 are 148×0 bits and 148×1 bits, and therefore 148×1 is selected and encoding processing is executed at TTI=40 ms. Further, the data to be transmitted on LCH1 is 8400 bits and the transport formats of TrCH2 are 336×0 bits, 336×1 bits, 336×2 bits, 336×4 bits, 336×8 bits, 336×12 bits, 336×16 bits, 336×20 bits and 336×24 bits. Since the format for the greatest number of bits is that for which 336 bits×24=8064 holds and, moreover, since 8064 bits×8400 bits holds, data is transmitted in the 336 bit×24 format in the initial TTI of 20 ms. In the next TTI of 20 ms, 8400−8064=336=336 bits×1 holds and therefore data is transmitted in the 336 bit×1 format. After TTI selection processing of TrCH1, TrCH2, encoding processing of each TrCH is executed and TrCH multiplexing is carried out.
FIG. 22 illustrates the amount of user data, after TrCH multiplexing, along a time axis. Over time {circle around (1)}, TrCH1: 148 bits×1 (TTI=40 ms holds, and therefore one-fourth of the data) and TrCH2: 336 bits×24 (TTI=20 ms holds, and therefore one-half of the data) is multiplexed. Over time {circle around (2)}, TrCH1: 148 bits×1 (TTI=40 ms holds, and therefore one-fourth of the data) and TrCH2: 336 bits×24 (TTI=20 ms holds, and therefore one-half of the data) is multiplexed. Over time {circle around (3)}, TrCH1: 148 bits×1 (TTI=40 ms holds, and therefore one-fourth of the data) and TrCH2: 336 bits×1 (TTI=20 ms holds, and therefore one-half of the data) is multiplexed. Over time {circle around (4)}, TrCH1: 148 bits×1 (TTI=40 ms holds, and therefore one-fourth of the data) and TrCH2: 336 bits×1 (TTI=20 ms holds, and therefore one-half of the data) is multiplexed.
Control for Selection of TFC Based Upon Transmission Power
3GPP TS25, 321 stipulates that the transport format combination TFC be selected in such a manner that the maximum transmission power of the mobile terminal will not be exceeded. TFC selection control usually considered in order to satisfy the above stipulation will now be described.
In a W-CMDA system that complies with the 3GPP standard, the following processing is executed when data (uplink data) is transmitted from a mobile terminal to a base station:
The transport format combination (TFC) of each transport channel TrCH is decided, user data is defined as DPDCH via TrCH encoding processing and TrCH multiplex processing, and transmission processing is executed.
Initial transmission power at the time of transmission processing is decided by a value (“initial.power”) reported from the higher layer beforehand. The gain-factor calculation unit 4 (FIG. 13) calculates the gain factors βd, βc, which are transmission-power control factors, frame by frame in accordance with the amount of data transmitted, and the multipliers 9c, 9d of the modulator 9 multiply the user data DPDCH and control data DPCCH, which are obtained after spreading, by the gain factors βd, βc, respectively, thereby applying weighting. The value of one of the gain factors βd, βc is always 1, and it is so arranged that βd and βc will fall within the ranges 0 to 1.0 and 0.0667 to 1.0, respectively, thereby indicating the relative ratio between then DPDCH and DPCCH power values.
The gain factors βd and βc are parameters that vary in dependence upon the amount of user data. The gain factor βd approaches 1.0 when the amount of user data increases, approaches zero when the amount of user data decreases and becomes zero when there is no user data. Conversely, βd, βc do not change if the amount of user data does not change.
A Rate Matching Attribute (referred to below as the “rate matching ratio”, or “RM ratio”), which is specified beforehand by the higher layer on a per-TrCH basis, is used to decide the gain factors βd, βc. The higher layer gives βdref and βcref as reference gain factors for any combination (TFC). In accordance withKref=Σi RMi×Nrefi  (1)the following equation:
                    Kref        =                              ∑                                                                      ⁢              i                                                                      ⁢                                          ⁢                      RMi            ×            Nrefi                                              (        1        )            where {circle around (1)} i represents the number of each TrCH, {circle around (2)} data length after encoding processing of each TrCHi is calculated is Nrefi represents this value, and {circle around (3)} Rmi represents the RM ratio of TrCHi, the gain-factor calculation unit 4 obtains the sum total of data lengths Rmi×Nrefi prevailing prior to rate matching processing of each TrCHi with respect to the reference combination. Similarly, after the selection of the jth transport format combination, the gain-factor calculation unit 4, in accordance with the following equation:Kj=ΣiRMi×Nji  (2)
                    Kj        =                              ∑            i                                                          ⁢                                          ⁢                      RMi            ×            Nji                                              (        2        )            obtains the sum total of data lengths RMi×Nji prevailing prior to rate matching processing of each TrCHi with respect to a TFCj to be actually transmitted.
Next, the gain-factor calculation unit 4 obtains Aj by the following equation:
                    Aj        =                                            β              ⁢                                                          ⁢              dref                                      β              ⁢                                                          ⁢              cref                                ×                                    Kj              /              Kref                                                          (        3        )            If the result of calculation is that Aj>1 holds, the largest value is selected from Table 1 below within the limits of βd=1.0 and βc≦1/Aj (if βc=0 holds, then a conversion is made to βc=0.0667). On the other hand, if Aj≦1 holds, the smallest value is selected from Table 1 within the limits of βc=1.0 and βd≧Aj. When the gain factors βd, βc are found, the transmission power value Pt is determined from Equations (4) to (8) below.
TABLE 11.00.93330.86660.80000.73330.66670.60000.53330.46670.40000.33330.26670.20000.13330.06670
After the channel is opened, the transmission power controller 11 obtains the DPCCH transmission power value PDPCCH and DPDCH transmission power value PDPDCH from the initial transmission power value initial.power and a minimum power value rang.mini, which are designated beforehand by the higher layer, in accordance with the following equations (see FIG. 23):PDPCCH=initial.power−rang.mini (dBm)  (4)PDPDCH=(βd/βc)×PDPCCH(dBm)  (5)Further, the transmission power Pt is given by the following equation:Pt=PDPDCH+PDPCCH(dBm)  (6)
Further, a base station measures the channel quality of uplink data transmitted from a mobile station, determines whether a target channel quality has been attained and, on the basis of the determination, instructs the mobile station to raise or lower the transmission power of the uplink slot by slot by a TPC bit, which is one item of control information in the downlink data. The amount of increase or decrease (power-up step=power-down step, where “step” is a power parameter) at this time also is specified by the higher layer. That is, “0” is inserted in the TPC segment of each slot shown in FIG. 16 if channel quality is good, and “1” is inserted if channel quality is poor. On the basis of the TPC bit segment of the downlink, the transmission power controller 11 of the mobile station controls the transmission power value Pt slot by slot in accordance with the following equations using the power-up step and power-down step (dB) specified beforehand by the higher layer:when TPC bit=0: Pt=Pt−step(dBm)  (7)when TPC bit=1: Pt=Pt+step(dBm)  (8)
FIG. 23 illustrates an example of the fluctuation in transmission power at the mobile station. Here time is plotted along the horizontal axis, and Pt represents the transmission power, rang.max the maximum transmission power reported from the higher layer beforehand, initial.power the initial transmission power reported from the higher layer beforehand, and rang.mini the minimum transmission power reported from the higher layer beforehand. It will be understood that uplink transmission power fluctuates, slot by slot, from the initial.power owing to control based upon the TPC bit.
FIG. 24 is a control processing flowchart for selecting TFC in such a manner that the transmission power value Pt will not exceed the maximum transmission power.
Before the channel is opened, the higher layer gives notification of the following: {circle around (1)} the initial transmission power value initial.power, which is a power parameter; {circle around (2)} the minimum transmission power value rang.mini, which is a power parameter; {circle around (3)} the maximum transmission power value rang.max, which is a power parameter; {circle around (4)} the power-up and power-down step, which is a power parameter, based upon the TPC bit; {circle around (5)} the reference gain factors βd, βc; {circle around (6)} the TrCH-LCH connectability status, transmission time interval TTI and transport format information (TFI table), which are TrCH parameters; and {circle around (7)} the RM ratio. Accordingly, these are received and saved (step 1001).
Next, when the TAF units 1a to in and host application 2 generate user data, these items of user data are collected in the TAF IF 3 and the latter selects the transport format combination TFC that will provide the highest throughput possible using the TrCH parameters (step 1002).
Next, by using the TrCH parameters from the selected TFC, the gain-factor calculation unit 4 calculates the gain factors βd, βc in accordance with Equations (1) to (3) and inputs these gain factors βd, βc to the modulator 9 and transmission power controller 11 (step 1003).
Using Equations (9) to (11) below, the transmission power controller 11 estimates a maximum value Pt13 max of transmission power (step 1004). Specifically, the transmission power controller 11 calculates the transmission power value Pt from the power parameters and gain factors βd, βc in accordance with the following equation:Pt=(1+βd/βc)×(initial.power−rang.mini)  (9)The larger βd/βc, i.e., the greater the amount of data, the larger Pt becomes. Furthermore, if we let step_max represent a maximum power-up step (relative to the power parameter “step”) per frame, we obtain the following because one frame is composed of 15 slots:step_max=step×15  (10)Therefore, the transmission power value Pt_max estimated to be the maximum per frame is found from Equations (9), (10) by the following equation:Pt_max=(1+βd/βc)×(initial.power−rang.mini) +step×15  (11)
Next, the transmission power controller 11 determines whether Pt_max exceeds the maximum transmission power value range.max (step 1005) and, if the decision rendered is “YES”, so notifies the TAF IF 3. In response, the TAF IF 3 changes TFC by the processing of step 1002, and the gain-factor calculation unit 4 and transmission power controller 11 repeat the processing from step 1003 onward. If a TFC according to which range.max is not exceeded is eventually selected, then the mobile station multiplexes and transmits the transport data of each TrCH based upon this TFC (step 1006).
With the prior-art method, a TFC is selected, transmission power is estimated after the calculation of the gain factors, it is determined whether the estimated transmission power exceeds the maximum transmission power range.max, and it is required that the TFC be re-selected if the maximum transmission power is exceeded. With the prior-art method, therefore, a large number of repetitions and a large number of processing steps are needed to decide a TFC according to which transmission power will not exceed the maximum transmission power range.max. A problem which arises is that the TFC cannot be decided at high speed. In addition, since the total number of processing steps is large, the end result is an increase in power consumption.
Further, a W-CDMA system is such that the smaller the total thermal noise due to the transmission power of a plurality of mobile stations present in the same cell, the greater the communication traffic can be made. The method of selecting TFC based upon transmission power according to the prior art is such that if mobile stations having different user-data transmission capabilities are mixed in one and the same cell, a situation arises in which mobile stations having a high transmission capability transmit upon selecting the TFC that results in maximum transmission power. In such case there is an increase in the total thermal noise within the cell and the base station limits the maximum transmission power of the mobile stations whose transmission capability is low. As a result, a limitation is imposed upon communication traffic.